As the date for my sourdough workshop draws closer, I have been in a frenzy of experimentation. I'm quite happy bumping along making bread in an intuitive and somewhat inconsistent manner, tolerating the odd failure, the occasional underproved or overproved loaf and so on, but I've realised that if I am to teach others how to make sourdough then I need to make the whole process a little more precise. I've tried out a couple of different proving routines, but have come to the conclusion that the most important issue is making sure that the shaped loaves are proved neither for too long nor for too little.
Most recipes tell you to prove dough "until it has doubled in size", which sounds find in theory, but in practice is almost totally useless. Without measuring, it is impossible to judge whether the loaf you are looking at now is double the size of the one you looked at 6 hours ago. (In fact, I have now extended my proving a little, so that the growth factor is around 2.5.)
Other recipes try to get round this by telling you how long to allow the dough to prove for. This sounds fine, except that we are talking sourdough time. In other words, the length of time your sourdough needs to prove for varies according to temperature: 4 hours proving at 21oC is not the same as 4 hours at 19oC or at 23oC. This is not so much of a problem in temperate countries with centrally heated housing, where the indoor temperature is fairly constant all year round, and you can set the proving times accordingly. However, I don't have either central heating or air conditioning in my kitchen in Cadiz, with the result that daytime kitchen temperatures go from about 15oC during a cold spell in the winter (as I write) up to the mid-20s in June or September. (I'm never here in July or August, but the temperatures must push up into the high-20s or beyond.)
So I decided that, to measure sourdough time, I needed a sourdough clock. The principle is simple:
- Get a narrow, straight sided, transparent container - a small plastic water bottle works fine.
- Just before shaping your dough, remove 100g of it, roll it a little to make it into a ball, place it in the bottom of the 'clock' and tamp it down a little with the handle of a wooden spoon.
- Attach a ruler to the side of the clock with two elastic bands, putting one elastic band level with the top of the dough.
- Using the ruler as a scale, put the other elastic band at the height above the first one which corresponds to your growth factor. The second line marks the point at which your dough will be ready to bake. (I am currently proving white sourdough by a factor of 2.5, so if my initial lump of dough comes up to 3 cm, then the second line would be set at 7.5 cm.)
- Cover the top of the sourdough clock with cellophane and keep next to your proving loaves. A little before the dough has reached its mark, you should turn the oven on to heat up.
I designed this as a useful aid for the novice baker, but have realised that it's also very helpful for more experienced bakers when trying out new bread recipes, making changes to existing ones, adjusting proving routines, or keeping a track on how seasonal changes in kitchen temperatures affect proving times.